Flexible skirting assemblies for ground effect machines



O United States Patent [111 3,536,156

[72] Inventor William Arthur Crago 3,373,839 13/1968 Hardy et a1. 180/128 Yeovil, Somerset, England 3,399,744 9/1968 Hopkins 180/128 [21] Appl. No. 730,858 3,416,627 12/1968 Francis et al. 180/127 [22] Filed May 21,1968 3,478,836 11/1969 Eckered et a1 180/128 [45] Patented Oct. 27, 1970 [73] Assignee British Hovercraft Corporation Limited jzz zgi fig 'zg 2 18? 2: :5 S

Yeovil, Somerset, England [32] Priority June 6, 1967 133] Great Britain [3 1 I 26,140/67 ABSTRACT: A flexible skirt assembly for ground effect 5 FLEXIBLE SKIRTING ASSEMBLIES FOR GROUND machines includes independent segments Whitih fOllTl the EFFECT MACHINES lower part of the skirt. Arrangements are prov ded for sup- Chin, 4 Drawing Fi's porting the segments, wherein a first diaphragm 18 attached to the rigid part of the machine so that it is inflated by CUSl'llOli- {52] US. Cl 180/128, generating i to form a chamber, and a second diaphragm is 180/ 127 attached in part to the first diaphragm and is also inflated to [51] lnt.Cl 860v l/l6 f a chamber The Second diaphragm forms one of the {50] Field of Search 180/ 127, mounting points f the se8mems various forms of the second diaphragm, particularly as to the manner in which it is connected to other components of the assembly, are rovided References cued so that the outer attachment point of the segments ma be out- UNITED STATES PATENTS board of the rigid structure of the vehicle, or the segments 3,333,650 3/1967 Hardy et a1. 180/128 may have a simpler configuration Patented" Oct.2 7,1970 1 3,536,156

shet L of a FLEXIBLE SKIRTING ASSEMBLIES FOR GROUND EFFECT MACHINES This invention relates to flexible skirt assemblies for ground effect machines, the skirt assembly acting as a barrier to the dissipation of one or more pressurized fluid cushions by which the machine is supported. More particularly, it related to improvements in methods of construction of flexible skirt assemblies.

l have discovered that to obtain optimum performance from a ground effect machine there is an ideal height for the skirt assembly, this height being a ratio of the dimensions of the air cushion space. I have also discovered that in skirt assemblies of the type consisting of a plurality of independent flexible segments depending from an upper inflatable member, there is an ideal ratio between the height of the segments and the total height of the skirt assembly. I have also found that there is an optimum ratio of segment width to segment height.

By the term segments I mean that part of the skirt assembly which is of corrugated form in plan view, wherein the webs of each individual corrugation are not joined to the webs of adjacent corrugations, as described in British Pat. No. 952,772 (U.S. Pat. No. 3,2l 1,246).

When these parameters combine to give a segment which is tall in proportion to the overall height of the skirt, the upper inflatable member becomes smaller relative to the segment, giving less room for the spacing of the segment attachment points, and thus the provision of suitable attachment points for ideal size segments becomes more difficult.

it is an object of this invention to provide a flexible skirt assembly having adequate attachment points for segments generally large in proportion to the total height of the skirt assembly.

In a skirt assembly of the type which includes an upper flexible inflatable member, because of the elasticity of pressurized air and the flexibility of the upper member, the skirt assembly has a natural vibratory period which may allow the skirt assembly to vibrate when it is pressurized to the normal operating pressure. Such vibration may have a deleterious effect, and

l have discovered that with the type of skirt assembly which I am proposing this occurrence is substantially eliminated.

lt is further object of this invention to provide a skirt assembly which has a natural frequency of vibration that is not critical to the optimum performance. 1

According to the invention I provide a flexible skirt assembly including a first diaphragm arranged for attachment to rigid structure of a vehicle, a second diaphragm attached at least in part to said first diaphragm, and a plurality of juxtaposed flexible segments depending in part from said second diaphragmv The second diaphragm maybe attached at two of its opposite edges to the said first diaphragm. or it may be attached at one edge to the said first diaphragm and at its opposite edge to the said flexible segments, or to rigid structure of a vehicle.

From another aspect of the present invention I provide a ground effect machine, having a flexible skirt assembly which acts as at least part of a barrier to restrict the dissipation of at least one pressurized fluid cushion by which the machine is supported, said skirt assembly including a first diaphragm which extends across a pressurized fluid discharge duct and is attached to rigid structure of the machine, a second diaphragm attached at least in part to said first diaphragm, and a plurality of juxtaposed flexible segments depending in part from said second diaphragm.

The second diaphragm may be attached at one of its edges to the first diaphragm and at the opposite edge to rigid structure of the vehicle, or it may be attached at each of its edges to r the first diaphragm, and the space enclosed by said first and second diaphragms may be inflated by pressurized fluid supplied to said space through at least one orifice in the said first diaphragm.

If desired, at least one further orifice may be provided in the said first diaphragm, through which pressurized fluid may flow to supply the pressurized fluid cushion, and at least one further orifice may be provided in the second diaphragm through which fluid may flow out of the space enclosed by the said first and seconddiaphragms.

The flexible segments preferably depend in part from said first diaphragm and in part from said second diaphragm. Alternatively, they may depend in part from the second diaphragm and in part from rigid structure of the machine.

The attachment points for the said first diaphragm and the said flexible segments to the rigid structure of the machine may be spaced apart.

if desired, each segment may be of an open channellike cross section, the inner surfaces of which face the supporting cushion, such that the pressure of the supporting cushion acts to maintain the segments in its operational position. Alternatively, each segment may be of a closed channellike cross section, in which case pressurized fluid may be fed to the interior of the segment. In the latter case, an orifice or orifices may be provided in the lowermost extremity of the segment.

The invention will now be described by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a section of a flexible skirt assembly according to one embodiment of the invention, wherein the second flexible diaphragm is attached in part to the first flexible diaphragm and in part to rigid structure of the machine;

FIG. 2 is a section of a flexible skirt assembly similar to that shown in FIG. I, but wherein the flexible segments depend in part from rigid structure of the machine;

FIG. 3 is a section of a flexible skirt assembly according to another embodiment of the invention, wherein the second flexible diaphragm is attached at two opposite edges to the first flexible diaphragm; and

FIG. 4 is a section of a flexible skirt assembly according to still another embodiment of the invention, in which the second flexible diaphragm is attached in part to the first flexible diaphragm and inpart to the flexible segments.

In the embodiment of the invention shown in FIG. 1, a flexible skirting assembly has a perforated flexible diaphragm l attached to the rigid buoyancy chamber 8 of a ground effect machine at point ll, and to the rigid structure of the outer duct wall 9 at a point 10 by any suitable releasable attachment means. The diaphragm l defines in part a chamber 12.

A second flexible diaphragm 13 is releasably attached to the outer duct wall 9 at a point 14 and to the perforated flexible diaphragm at a point 15. The second flexible diaphragm defines in part an inflatable chamber 4, and extends laterally outwards beyond the rigid parts of the machine.

Segments 2 which are of a closed channellike cross section having an orifice 17 at their lower tip depend below the chambers l2 and 4, and are releasably attached to the perforated I flexible diaphragm 1 at a point 3 and to'the flexible diaphragm 13 at a point 5. Segments of this type are preferably used at the bow and the stern of the vehicle, in order to prevent scooping when operating over water. However, they are not limited to these positions, and may be used at any position on the vehicle.

lnoperation, pressurized fluid is fed from the fluid supply means (not shown) through ducts in the rigid part of the vehicle to the chamber 12, the path of the fluid into the chamber being generally as represented by arrow 18. The fluid passes through the orifices 7 into the segments 2 and issues from the orifices 17 in the lower tip of the segments to supply the fluid cushion l6. Fluid also passes from the chamber 12 by way of orifices 6 to inflate the chamber 4.

In the embodiment of the invention shown in FIG. 2, the segments 2 are of an open channellike cross section with the inner surfaces of the channellike cross section facing the fluid cushion 16. The segment is attached to the flexible diaphragm '13 at a point 5 and to the rigid buoyancy chamber 8 at a point 3. Segments of this typeare preferably used along the sides of the vehicle, but they are not limited to these positions. When segments of this type are used on the sides of the vehicle they may be interspersed with segments similar to those generally described in connection with FIG. 1.

in operation, the fluid flows from thechamber 12 by means of orifices 7 to the top of the segments. and issues into the fluid cushion area 16. The segment is inflated partly by the fluid flowing from theorifices 7 and partly by the fluid cushion pressure. p

Referringnow to the embodiment of the invention shown in releasable attachment means. lnthis embodimennhowever,

the second flexible diaphragm 13 is connected at its two op posite edges to the flexible diaphragm l at points 14 and 15. v The flexible segments 2 depend below the chambers 4 and 12,

' and are releasably attached to the-flexible diaphragm l at a point 3 and to the second flexible diaphragm 13 at a point 5.

In operation, pressurized fluid passes from the chamber 12 v through orifices 61o inflate the chamber 4. Thus the pressures in the chambers 4 and 12' are substantially the same. Further.

orifices 19 are provided in the diaphragm 13, to allow pressurized fluid to passt'rom the chamber 4 into the segments 2. Additional orifices 7 are provided in the diaphragm I. through which pressurized fluid is supplied from the chamber 12 direct to the segment 2 or the fluid cushion l6. p it is to be understood that, if desired, the second flexible diaphragm 13 need not be provided with orifices, l9, pressurized fluid being fed to the fluid cushion 16 by way of the orifices 7 only. Alternatively; the additional orifices 7 need not be supplied in the flexible diaphragm l, pressurized fluid being fed tothe fluid cushion l6 byway of the orifices 19 in the second flexible diaphragm 13. w

ln anotherembodiment of the invention shown in F [0.4,

the second flexiblediaphragm .13 isattached .rd'me flexible The orifices in the second flexible diaphragm may be so positioned that they supply fluid to the segments, direct to fluid cushion, or to the outside of the skirt assembly for purposes of skirt lubrication.

[claims I l. Aflexible skirt assembly for'a ground efi'ectmachine comprising. afirst. diaphragm of impermeable material .arranged for attachment of one of its edges to rigid structure of the machine at a relatively inboard location and the opposite one of its edges to rigid structure of the machine at a location substantially outboard of said inboard location to define at least part of a first chamber; a second diaphragm of impermeable material attached at least alongprie edge to said, first diaphragm; a pluralityof substantially independent juxtaposed flexible segments depending at least in part from said second diaphragm, each flexiblesegment beingcapable of generally independent movement relative to adjacent segments; theo'pposite edge of said second diaphragm being arranged for condiaphragm l at a point 14. and its opposite edge is attached to the flexible segment 2 at a points. The flexible segment '2 is ment the diaphragm l, isshown connected to the rigid structure of the outer duct wall .9 at a point to which isabove the bottom edge of the outer duct wall, and to the rigid buoyancy chamber-8 at a point ll which is inboard of the outer edge of .35 also attached to the diaphragm l at apoint 3. ln thisembodi- In operation, pressurized fluid passes from the chamber' l2 1 through theorific'es 6 in the'flexiblediaphragm'l to the space 4 enclosed by the flexiblediaphragms l and I3. and the top of the flexible segments 2. The pressurized fluid dissipates from this spaee into the flexible segments 2. Further orifices 7 are providedin the flexible diaphragm [through which pressurized fluid passes from the chamber 12 directly to the H cushion space'l6.

Although four. embodiments ofthe invention have been described, the invention is not limited to the embodiments, and many modifications are possible. For example, in the embodiments shown in;FlGS.l and 2.valve means may be provided in the orifices 6, to retain the pressure in the chamber 4 afier the fluid supply means has been closed down. Alternatively, in the embodiment of F I65. 1 to 3; the chamber4 could j be inflated from an independent source. The skirts described could be used as stability. barriers to divide. the supporting cushion into a number of subcushions.

The flexible skirt assembly described uses a flexible diaphragm 1 provided with orifices through which pressurized fluid flows to feed the supporting cushion. However, it is to be understood that the pressurized fluid supplying the supporting n I cushion need not flow through the flexible fdiaphra'gm, but.

may be fed at any convenient location. The chambers 4 and 12.

may then be pressurized fromthe same source of supply as n that which supplies fluid for the fluid supporting cushion, the. fluid being fed to the cushion by a separate duct. Alternatively,.the sources of supply of the pressurized fluid to the supporting cushion and to the skirt assembly may be difierent.

said opposite edge to rigid structure of the machine in the general area of said outboard location.

3. A flexible. skirt assembly as clalmedin claim 2 wherein said flexible segments are connected to said first diaphragm and said second diaphragm at different locations. t

4. A flexible skirt assembly as' claimedin claim 2 wherein said flexible segments are connected to said seconddiaphragm and arranged for connection to rigid structure of the machine.

5. A flexible skirt assembly as claimed in claim 1 wherein said second diaphragm is attached along its said one and opposite edges to said first diaphragm at separate locations so as to define said second chamber together .with said first diaphragm.

6. A flexible skirt assembly as claimed" in claim 1 wherein the oppositeedge .of said second diaphragm is connected to said flexible segments.

7. A flexible skirt assembly as claimed. in claim l'lurther comprising orifice meansin said first diaphragm for commui icating said first chamber with said second chamber.

8. A flexible skirt assembly as claimed in claim 7 further comprising orifice meansin said firstdiaphragm for commu- 1 nicating said first chamber with said flexible segments.

9. In a ground eifect machine having a rigid body structure and atleastone pressurized fluid discharge duct for at least partially creating .a pressurized fluid cushion under the machine, and a flexible skirting assembly which acts as at least part of a barrier to restrict the dissipation of the fluid cushion, said skirt assembly comprising a first diaphragm of impermeable material which extends across a pressurized fluid discharge duct and defines at least part of a first chamber, said first diaphragm being attached at one of its edges to rigid structure g of the machine at a relatively inboardlocation and at the opposite one of its edges to rigid structure of the machine at a location substantially outboard of said inboard location, a

second diaphragm of impermeable material attached at least along one edge to said first diaphragm, a plurality of juxtaposed, substantially independent, flexiblesegments depending at least in part from said second diaphragm, each flexible segment being capable of substantially independent movement'relative to adjacent segments, and the opposite edge of said second diaphragm being connected to one member of the assembly consisting of rigid structure of the machine, said first diaphragm, and said flexible segments to form at least part of a second chamber. 1

. 10 A flexible skirt assembly as claimed in claim 9 wherein said second diaphragm is connected. aiong'its said opposite edge to rigid structure of the machine in the general area of saidioutboard location.

:11. A flexible skirt assembly 'as claimed in claim 10 wherein flexible segments are connected to said second diaphragm and to rigid structure of the machine. 1

12. A ground efl'ect machine as claimed in claim 11, wherein the attachment points of the segments and the attachment points of the first flexible diaphragm on the rigid structure of the machine are spaced apart.

13. A ground effect machine as claimed in claim 9 wherein the second chamber is inflated by pressurized fluid supplied to said second chamber through at least one orifice in the said first diaphragm.

14. A ground effect machine as claimed in claim 13, wherein at least one further orifice is provided in the first diaphragm, through which pressurized fluid is supplied to the pressurized fluid cushion.

15. A ground effect machine as claimed in claim 9, wherein each segment is of open ehannellike cross section with the open side facing the supporting cushion so that the pressure of the supporting cushion acts on the inner surfaces of the segment, to maintain said segment in its operational position.

16. A flexible skirt assembly as claimed in claim 9, wherein each segment is of closed channellike cross section, and has an orifice at its lower end.

17. A flexible skirt assembly as claimed in claim 9, wherein pressurized fluid is supplied to the cushion area by a separate duct. 

